Improvements in excavator teeth

ABSTRACT

Abstract of the Disclosure 
         
   An excavator tooth system comprises a mounting nose having a projecting spigot and a wear member (12) having at one end a socket (18), the socket (18) being defined by spaced side walls and upper and lower walls converging from a rearwardly facing socket opening to a forward end of the socket.  Each of the upper and lower walls comprises a forward bearing face (8a) and a rear bearing face (7a) separated by a forwardly convergent intermediate face.  The front and rear bearing faces (8a,7a) are substantially parallel to a longitudinal axis (50) of the wear member and engage corresponding bearing faces (8,7) in said spigot.

Detailed Description of the Invention Background of Invention

[0001] This invention is concerned with improvements in excavator teethfor earth excavating devices.

[0002] The invention is concerned particularly, although notexclusively, with the mounting of excavator teeth adaptors to adaptornoses on an excavating device such as an excavator bucket or the like.

[0003] Excavating teeth mounted to the digging edge of excavator bucketsand the like generally comprise a replaceable digging point, an adaptorbody and an adaptor nose which is secured by welding or the like to thedigging edge of a bucket or the like. The adaptor has a socket-likerecess at its rear end to receivably locate a front spigot portion ofthe adaptor nose and a locking pin extends through aligned apertures inthe adaptor and nose to retain the adaptor in position.

[0004] In use, excavator teeth are subjected to extensive load forcesalong a longitudinal axis of a tooth as well as in vertical andtransverse directions. A snug fit is required between the digging pointand the front portion of the adaptor and also between the adaptor socketand the nose spigot portion and their respective mounting pins to avoidpremature wear between the components. As the various components wear,the locking pins can loosen thereby increasing the risk of loss of adigging point or an entire digging tooth assembly.

[0005] The greatest loads experienced by excavator teeth are verticalloads which tend to generate large moment forces capable of rotating atooth off the front of an adaptor and/or rotating the adaptor off theadaptor nose.

[0006] Despite many prior art attempts to improve the mounting of anadaptor to a nose, most of these proposals suffer from one or moredeficiencies.

[0007] United States Patent No 4,182,058 describes an excavator toothhaving a rearwardly divergent tapering socket to receive a nose having acomplementary-shaped front spigot portion. Resistance to rotationalmoment forces is borne by a resilient steel cotter pin extending throughaligned vertical apertures in the socket and spigot portions.

[0008] United States Patent No 3,023,521 also describes an excavatortooth having a rearwardly divergent tapering socket to receive acomplementary-shaped tooth support spigot portion. Rotational momentforces are resisted by a lip engaging in a recess in the tooth supportmember.

[0009] United States Patents 3,774,324, 4,338,736, 4,481,728 and4,903,420 all describe nose and tooth combinations wherein the nose hasa generally convergently tapering spigot portion with a forward tiphaving a box-like configuration with at least the upper and lowersurfaces thereof having faces parallel to each other and to alongitudinal axis of the nose portion. With the exception of Patent No4,338,736, which describes a transverse locking pin, each of the toothmounting arrangements is heavily reliant on a large vertical locking pinto resist rotational moment forces tending to rotate the teeth offrespective noses.

[0010] United States Patent No 4,231,173 describes a tapered adaptornose having a box-like free end, which engages in a mating box-likesocket cavity to resist rotational moments. Opposed pairs of rearwardlyextending tongues engage in corresponding recesses in the outer surfacesof the adaptor nose to resist rotational movements. Because the tonguesthemselves are unsupported, they possess a limited capacity to resistrotational moment forces.

[0011] United States Patent No 5,272,824 describes a structure similarto that of United States Patent No 4,231,173 except that the sidetongues are of more robust dimensions and the upper and lower tonguesare formed as box-like members with apertures to receive a verticalmounting pin passing through aligned apertures in the tooth and adaptornose.

[0012] United States Patents 3,196,956 and 4,404,760 provide flat railsurfaces on the adaptor nose to engage with mating grooves in the socketaperture of a corresponding tooth. In the case of Patent No 3,196,956,the mating rail and groove surfaces are forwardly tapered, whereas inPatent No 4,404,760 the mating rail and groove surfaces are generallyparallel to the longitudinal axis of a tooth.

[0013] United States Patent No 5,423,138 describes a generally taperednose having a box-like front end with upper and lower transversesurfaces generally parallel to a longitudinal axis of a tooth. Theparallel upper and lower transverse surfaces are contiguous with upperand lower rail surfaces on each side of the nose and parallel to thelongitudinal axis of the tooth. A pair of rearwardly extending sidetongues locate in recesses formed in the outer side faces of the nose,ostensibly to resist rotational moment forces in the tooth. Because theside tongues are recessed to accommodate the side rail portions, therobustness of the side tongues is somewhat compromised.

[0014] United States Patent No 4,233,761 describes a fairly stubbytapered nose having a box-like front portion with upper and lowersurfaces generally parallel to a longitudinal axis of an excavatortooth, an intermediate rearwardly diverging tapered portion and a rearportion having upper and lower surfaces extending generally parallel toa longitudinal axis of the tooth. Formed on the upper and lower surfacesof the front, intermediate and rear portions of the nose are spacedparallel reinforcing ribs which are located in mating grooves in theexcavator tooth. A large vertical locking pin extends through alignedapertures in the tooth and nose between the reinforcing ribs. Thisstructure is heavily reliant on the locking pin to resist rotationalmoment forces however it is considered that this configuration may beprone to failure in the rear portion of the adaptor.

[0015] United States Patent No 5,709,043 describes a nose/adaptorcombination wherein the adaptor socket tapers convergently towards abox-like front portion having upper and lower bearing surfaces generallyparallel to a longitudinal axis of the tooth, a front transverse uprightbearing surface and rearwardly divergent bearing surfaces formed atobtuse angles between the converging upper and lower walls and the sidewalls of the socket, ostensibly to avoid areas of stress concentration.

[0016] United States Patent No 6,018,896 describes a pin/retainer systemfor locking an excavation tooth onto an adaptor wherein the retainer isinserted in the adaptor and a wedge-shaped pin is driven into alignedapertures in the tooth and adaptor to resiliently engage with theretainer.

[0017] United States Publication No US 2002/0000053A1 describes amechanism for releasably retaining an adaptor into the nose of a bucketlip or the like wherein a tapered threaded socket is non-rotatablylocated on the inside of an aperture in the side wall of the adaptor. Athreaded retaining pin extends through the threaded socket and locatesin an aligned aperture in the bucket nose.

[0018] United States Patent No 5,337,495 describes a tooth pointslidably locatable over a tapered adaptor front portion, the tooth pointbeing releasably secured on the adaptor by a pair of cap screwsextending through apertures in the side walls of the tooth into threadedinserts located in recesses on opposite sides of the adaptor frontportion. The inserts have a shouldered face and a curved face nestablein complementary-shaped adaptor recesses to prevent rotation when thecap screws are threadably located therein.

[0019] United States Patent No 5,172,501 described attachment of adigging point to an adaptor by a threaded bolt extending through anaperture in a point for threaded engagement in a threaded opening in theadaptor. Other retention systems for digging points on adaptors oradaptors on noses are described in United States Patents Nos 6,119,378,6,467,204, 6,052,927 and 6,467,203.

[0020] Other devices for removably securing replaceable wear elements onearth working equipment such as a retaining pin, a bolt, a pin lock, aspool and wedge system or a flex pin are described in United StatesPatents Nos 3,839,805, 3,982,339, 4,587,751 and 5,716,667 respectively.

[0021] United States Patent No 5,937,550 describes a lock assembly forreleasably securing an adaptor to a nose of an excavator supportstructure. The lock assembly comprises a body and a base coupledtogether and adapted for insertion, while coupled together, in a hole inthe nose of the support structure. The length of the lock assembly isextended to secure the adaptor and is retracted to release the adaptor.While adequate for securing an adaptor to a nose of an excavator supportstructure, the lock described in this patent is relatively complex indesign and operation leading to high costs and labour intensiveextraction procedures in the field.

[0022] Canadian Patent Application No 2,161,505 describes a system forremovably retaining an excavation point on an adaptor with at least oneflanged sleeve having a screw-threaded aperture therein, the flangedsleeve being non-rotatably locatable in a transverse bore in the adaptorbefore fitment of the point onto the adaptor. A screw-threaded pin isinserted into the sleeve via an aperture in the point whereby portion ofthe head of the pin retains the point on the adaptor.

[0023] While generally satisfactory for their intended purpose, theabovementioned prior art adaptor/nose combinations all suffer from oneor more shortcomings or disadvantages in terms of inadequate resistanceto rotation of an adaptor off a nose under the influence of verticalloads applying a rotational moment to the adaptor, a predisposition topremature wear, difficulties in retention of the adaptors on noses,inadequate locking systems and unduly complicated configurations givingrise to increased fabrication costs.

[0024] It is an aim of the present invention to overcome or alleviate atleast some of the abovementioned prior art disadvantages or otherwise toprovide consumers with a convenient choice.

Summary of Invention

[0025] According to one aspect of the invention there is provided anexcavator tooth system comprising: a mounting nose having a projectingspigot; and a wear member having at one end thereof a socket, saidsocket being defined by spaced side walls and upper and lower wallsconverging from a rearwardly facing socket opening to a forward end ofsaid socket, each of said upper and lower walls comprising a forwardbearing face and a rear bearing face separated by a forwardly convergentintermediate face, said front and rear bearing faces being substantiallyparallel to a longitudinal axis of said wear member. Suitably, saidforward end of said socket forms an end bearing face.

[0026] If required, said end bearing face may extend transversely ofsaid longitudinal axis. The wear member may comprise an excavator toothhaving a digging edge at a front end thereof. Preferably, the wearmember comprises an adaptor having a front end adapted for releasableattachment of a digging point. Suitably, said wear member includes anaperture in at least one wall of said socket. Preferably, said wearmember includes aligned apertures on opposite walls of said socket. Ifrequired, said aligned apertures may extend through upper and lowersocket walls. Preferably, said aligned apertures extend through oppositeside walls of said socket. If required, at least portion of said rearbearing face is of a width greater than said forward bearing face. Atleast portion of said rear bearing face may be of substantially asimilar width to said forward bearing face. Suitably, said rear bearingface is of an area greater than said forward bearing face.

[0027] The socket opening may have a transverse width greater than thewidth of the forward end of said socket. If required, the side walls ofsaid socket may taper convergently towards said forward end of saidsockets. Alternatively, the side walls of said socket may be stepped.

[0028] According to another aspect of the invention there is provided anexcavation device having an excavator tooth system according to a firstaspect of the invention and wherein said mounting nose is integrallyformed with said excavation device. Alternatively, said mounting nosemay be attached to said excavation device. According to a further aspectof the invention there is provided a lip for an excavation device saidlip having a plurality of spaced mounting noses for excavator toothsystems according to a first aspect of the invention. Suitably, saidmounting noses are attached to said lip. Preferably, said mounting nosesare integrally formed with said lip. If required, said lip may includewear plates releasably secured between adjacent mounting noses.

[0029] According to a further aspect of this invention there is provideda lock for releasably attaching a wear member to a mounting nose of anexcavator bucket, said lock comprising: a retaining member having a headportion and a screw-threaded shaft; and an elongate body member having anon-circular cross section, said body member being adapted for removableinsertion in a lock aperture of complementary cross section in themounting nose, said body member including a screw-threaded aperture toreceivably locate said retaining member, said body member, in use, beingcaptively retained in said lock aperture by a partial misalignmentbetween said lock aperture and a retaining aperture in the wear memberwhen said wear member is located on said mounting nose, said retainingmember, in use, being releasably securable in said body member via saidretaining aperture whereby said head portion is located within saidretaining aperture to prevent disengagement between said mounting noseand said wear member.

[0030] Suitably, said head portion includes a tapered shoulder extendingbetween said head portion and said shaft, said tapered shoulder in usebeing frictionally engagable with a corresponding tapered recess in saidbody member. Suitably, said screw-threaded aperture is displaced fromthe central longitudinal axis of said body member. If required, saidlock may comprises a corrosion resistant coating. Optionally, said bodymember may be formed from a corrosion resistant material. Optionally,said body member may be formed from a rigid engineering plasticsmaterial. The plastics material may be selected from nylon, glass fillednylon, or the like. Optionally, retaining members are coupled with saidbody member at opposite ends thereof to secure the wear member on themounting nose.

[0031] According to yet a further aspect of this invention there isprovided a method of securing a wear member to a mounting nose of anexcavator bucket including: inserting a body member of a lock into alock aperture in said mounting nose, said body member having anon-circular cross sectional shape for location in a lock aperture ofcomplementary cross sectional shape in the mounting nose; captivelyretaining said body member in said lock aperture by locating a wearmember on the mounting nose whereby a retaining aperture in the wearmember is partially misaligned with said lock aperture in the mountingnose; and inserting, via said retaining aperture, a screw-threaded shaftof a retaining member into a screw-threaded socket in said body memberwhereby a head portion of said retaining member is located in saidretaining aperture to prevent disengagement between said mounting noseand said wear member. Optionally, retaining members are coupled withsaid body member at opposite ends thereof to secure the wear member onthe mounting nose. According to yet a further aspect of this inventionthere is provided a system for releasably retaining a wear member to amounting nose of an excavator bucket comprising: (a) a mounting nosehaving a non-circular lock aperture extending at least partially within;(b) a wear member having at least one retaining aperture which ispartially misaligned with the lock aperture in the mounting nose whensaid wear member is located thereon; and (c) a lock having a retainingmember with a head portion and a screw-threaded shaft; and a body memberhaving a non-circular cross sectional shape adapted for removableinsertion in said lock aperture in the mounting nose, said body memberhaving a screw-threaded aperture to receivably locate saidscrew-threaded shaft, wherein in use, said body member is captivelyretained within said lock aperture by partial misalignment of the lockaperture and the retaining aperture when the wear member is located onthe mounting nose and said screw-threaded shaft is securable within saidscrew-threaded aperture via said retaining aperture to locate said headportion within said retaining aperture to prevent disengagement betweensaid mounting nose and said wear member. Suitably, said screw-threadedaperture is displaced from the central longitudinal axis of said bodymember. Optionally, retaining members are coupled with said body memberat opposite ends thereof to secure the wear member on the mounting nose.

Brief Description of Drawings

[0032] In order that the invention may be more fully understood and putinto practical effect, reference will now be made to the accompanyingdrawings in which:

[0033]FIG. 1 shows portion of an adaptor nose;

[0034]FIG. 2 shows an exploded view of an excavator tooth systemaccording to one aspect of the invention;

[0035]FIG. 3 shows schematically an upright cross-sectional view showingthe engagement between a mounting nose and an adaptor according to theinvention;

[0036]FIG. 4 shows in transverse cross-section a locking pin forreleasable attachment of the adaptor to the mounting nose;

[0037]FIG. 5 shows in transverse cross-section the locking pin of FIG. 4in a locked position;

[0038]FIG. 6 shows schematically a transverse cross-sectional view of anexcavator tooth system according to one aspect of the invention;

[0039]FIG. 7 shows a lip for an excavation device in accordance withanother aspect of the invention;

[0040]FIG. 8 shows an exploded view of the lip of FIG. 7 and excavatorteeth systems according to one aspect of the invention;

[0041]FIG. 9 shows the arrangement of FIG. 8 in an assembled state;

[0042]FIG. 10 shows a lock for releasable attachment of the adaptor tothe mounting nose;

[0043] FIG 11 shows a longitudinal cross sectional view of a retainingmember of the lock of FIG 10; and

[0044] FIG 12 shows a longitudinal cross sectional view of a body memberof the lock of FIG 10.

Detailed Description

[0045] In the accompanying drawings, for the sake of clarity, likereference numerals are employed for like features where appropriate.

[0046] In FIG. 1, the mounting nose 1 is shown as integrally formed witha cutting lip 2 of an excavation device such as a dragline bucket or thelike (not shown). Nose 1 includes a pair of opposed generally parallelside faces 3, a front face 4 and upper and lower faces 5,6 convergingtowards front face 4. Upper and lower faces 5, 6 each include rearbearing faces 7 and forward bearing faces 8 separated by a taperedgenerally planar intermediate face 9. Rear bearing faces 7, forwardbearing faces 8 and front bearing faces 10 are all shown as shadedregions for the sake of clarity. Rear bearing faces 7 are parallel toeach other as are forward bearing faces 8. Each of rear and forwardbearing faces 7,8 are also parallel to a longitudinal axis X of themounting nose 1.

[0047] Extending transversely of mounting nose 1 is an adaptor mountingaperture 11. Aperture 11 is generally oval in cross-sectional shape withthe longer oval axis extending generally parallel to nose axis X.Aperture 11 is positioned closer to top face 5 than bottom face 4, thepurpose of which positioning will be described in detail later.

[0048] In a conventional tapered wedge-shaped adaptor nose there is asubstantial rotational moment to a digging point in the region of theadaptor tip. This rotational moment force is resisted by normallydirected forces in the rear of the upper and lower wedge faces andfrictional forces in the upper wedge face. If the rotational moment issmall compared with the normally directed forces on the upper wedgeface, the frictional forces produced by the normally directed forces canbe sufficient to withstand the rotational moment. For a digging pointthis usually is the case because as the moment force on the diggingpoint is applied almost directly above the upper face of the wedge, themoments are small compared to the normal forces and the correspondingfrictional forces are sufficient to retain the digging point in place.

[0049] In the case of the mounting between a wedge-shaped adaptor noseand the adaptor itself, the frictional forces are insufficient towithstand the rotational moment to prevent the adaptor from simplyrotating off the nose under load. To overcome this it is customary withwedge-shaped adaptor noses to employ a substantial pin to retain theadaptor in place as the pin must withstand very large forces appliedthereto. Typically, this necessitates a vertically oriented pin.

[0050] In the present invention, the key bearing faces are configured tobe generally parallel to the longitudinal axis of a wear member such asan adaptor. The wear member is thus cantilevered on the nose whereby therotational moment is resisted by the high load forces applied to theupper forward bearing face and the lower rear bearing face. Generallyspeaking the higher those load forces, the higher the friction availableto hold the adaptor or wear member onto the nose. Because the bearingfaces are substantially parallel, an adaptor cannot rotate off its nose.

[0051] The excavator tooth system according to the invention in effectbecomes self-locking by virtue of its high internal frictional forces.As a consequence, the role of the retaining pin is substantially reducedfrom being a major structural component in prior art systems to being adevice which simply stops the wear member from falling off a nose.

[0052]FIG. 2 shows an exploded view of an excavator tooth assemblyaccording to one aspect of the invention. As shown, the assemblycomprises a mounting nose 1 (shown partially), an adaptor 12 and areplaceable digging point 13. Adaptor 12 includes a hollow recess orsocket (not shown) to receive the nose 1. Adaptor 12 is retained on nose1 by a spool and wedge pin 14 which extends through oval-shapedapertures 15 in the adaptor body when aligned with aperture 11 innose 1. Point 13 is releasably retained on the front tip of adaptor 12by a retaining pin (not shown) extending through aligned apertures 16,17in the point 13 and adaptor 12 respectively.

[0053] FIG 3 is a schematic vertical cross-sectional view through thenose 1 and adaptor 12 of FIG. 2 and shows the engagement of the bearingsurfaces of the nose and adaptor. When the spool and wedge pin 14 istensioned nose 1 is firmly located in the socket cavity 18 of adaptor 12with the front bearing face 10 of nose 1 in abutment with correspondingbearing face 10a in adaptor 12. Similarly, rear and forward bearingfaces 7 and 8 are abutted against corresponding bearing faces 7a, 8arespectively in adaptor 12.

[0054]FIG. 4 is a partial schematic transverse cross-sectional viewthrough the nose/adaptor combination shown in FIG. 3. As shown, spooland wedge retaining pin 14 is in an extended unlocked position with theshoulders 20 of pin body 21 being located behind the rear inner edges ofapertures 15. A threaded bolt 22 is rotatably journalled in one end ofpin body 21 and its other end is engaged in a threaded aperture 23 inwedge member 24. As bolt 22 is rotated, it draws wedge member 24 intothe aligned apertures 15,11 of adaptor 12 and nose 1 respectively untilit wedges adaptor 12 into tight engagement with nose 1 as shown in FIG.5.

[0055] As can be seen in FIG. 5, retaining pin 14 is in a retractedlocking position with the free ends thereof slightly recessed intoapertures 15.

[0056]FIG. 6 shows a schematic transverse cross-sectional view throughthe assembly of FIG. 2 when in an assembled state.

[0057]FIG. 7 shows another aspect of the invention. Depicted is acutting lip 30 of an excavation device such as a dragline bucket (notshown). Cutting lip 30 is cast as an integral component from a suitablywear resistant metal alloy and comprises a transverse cutting bar 31,cheek plates 32 and mounting noses 1 at spaced intervals therealong.Noses 1 are faired back into cutting bar 31 forming recessed regions 33between adjacent noses. At the front portion of each cheek plate 32 aremounts 34 for attachment of replaceable cutting edges (not shown).

[0058]FIGS. 8 and 9 respectively show an exploded view and an assembledview of the cutting lip 30 of FIG. 7 with adaptors 12 and digging points13 of FIG. 2.

[0059] In the assembly of FIG. 9, lip shrouds 35 are removably securedin the recessed regions of bar 31 to minimize wear on the lip assembly.As can be seen from FIG. 9 and also from FIGS. 1 and 3, the aligned pinapertures 11,15 of nose 1 and adaptor 12 respectively are displacedvertically upward relative to a transverse plane occupied by thelongitudinal axis X as shown in FIG. 1, which axis lies in a centralplane of nose 1. By having the mounting apertures offset from a centralposition, the retaining pins can be removed or installed without needingto remove the lip shrouds 35. In turn, this permits the face of the lipshroud 35 to be located at its optimal position with the face of theshroud running along the centre line of the tooth assembly.

[0060] It readily will be apparent to persons skilled in the art thatmany variations and modifications may be made to the invention withoutdeparting from the spirit and scope of the invention.

[0061] For example, as the key digging forces are taken up by the socketand spigot fitting between the nose and the wear member or adaptor; theretaining pin can be of any design as it functions merely to hold thewear member in place on the nose and otherwise does not constitute aload bearing member.

[0062] FIG 10 shows lock 36 being an alternative embodiment of a lockingpin.

[0063] FIG 11 shows a longitudinal cross sectional view of the retainingmember 38 illustrated in FIG 10.

[0064] FIG 12 shows a longitudinal cross sectional view of the bodymember 37 of FIG 10.

[0065] As shown in FIGS 10 to 12 the locking pin 36 comprises a bodymember 37 wherein the body has an oval shaped cross section ofsubstantially identical configuration as the cross sectional shape ofaperture 11 in mounting nose 1 as illustrated in FIG 3. As can be seenin FIG 10, the centre of screw-threaded aperture 45 is displaced fromthe intersection of the longer and shorter axis of the oval shaped crosssection of body member 37. However, the centre of screw-threaded shaftremains on the longer axis, the reason for which will be discussed indetail below.

[0066] In use, both of retaining members 38 are withdrawn from eachscrew-threaded aperture 45 of body member 37 independently of mountingnose 1. Body member 37 is fully inserted into aperture 11 on mountingnose 1 of an excavator bucket as shown in FIG 3, FIG 4 and FIG 5.Adaptor 12 is then located on mounting nose 1. As seen in these figures,aperture 15 on adaptor 12 is partially misaligned with aperture 11 onmounting nose 1 when adaptor 12 is located on mounting nose 1. Thispartial misalignment captively retains body member 37 within aperture 11while mounting nose 1 is located on adaptor 12. Furthermore, body member37 is prevented from rotating within aperture 11 due to the oval shapedcross section of body member 37 being complementary with oval shapedaperture 11.

[0067] Referring specifically to FIG 4 and FIG 5, even though bodymember 37 is captively retained within aperture 11 due to themisalignment of aperture 11 and aperture 15, screw-threaded aperture 45of body member 37 is still not covered by adaptor 12 and hence remainsaccessible. This is due to screw-threaded aperture being offset from thecentre of body member 37 as described above.

[0068] To retain adaptor 12 on mounting nose 1, retaining members 38 areinserted through apertures 15 and 11 at opposite ends of body member 37such that the screw-threaded shaft 41 of each retaining member iscoupled with the screw-threaded aperture 45 at either end of the bodymember 37. When tapered shoulder portion 40 abuts tapered recess 44, atleast some of head portion 39 is located within aperture 15 on eitherside of adaptor 12. This protrusion of the head portion 39 at either endof lock 36 prevents adaptor 12 from sliding off mounting nose 1. Asdiscussed above, lock 36 may be used with only a single retaining member38 to retain adaptor 12 on mounting nose 1.

[0069] To remove adaptor 12 from mounting nose 1 retaining members 38are decoupled from body member 37. This is facilitated by removingscrew-threaded shaft 41 of each retaining member 38 from screw-threadedaperture 45 at either end of body member 37. Adaptor 12 can then beremoved from mounting nose 1 as head portion 39 of each retaining member38 no longer retains the adaptor on the mounting nose. Once adaptor 12has been removed, body member 37 can be extracted from aperture 11.

[0070] Lock 36 is self-locking and self-aligning due to the abutment oftapered shoulder portion 40 with tapered recess 44. This tapered contactprovides for greater frictional gripping between body member 37 andretaining member 38 than a conventional square shouldered contact. Aperson skilled in the art will recognise the analogy between the taperedcontact made between retaining member 38 and body member 37 and theconfiguration of a wheel nut. Hence, retaining member 38 remains insecure contact with body member 37 while in use and retains adaptor 12on nose 1. When it is necessary to remove adaptor 12 from nose 1 thetapered contact provides for an easy release of retaining member 38 frombody member 37 thus reducing the time necessary to change the adaptorleading to increased efficiency.

[0071] Furthermore, the tapered contact accounts for manufacturingtolerances of member 37 and retaining member 38 as the lock isself-aligning when tapered shoulder portion 40 proceeds into taperedrecess 44, and the retaining member is tightened, the tapered contactguides retaining member 38 and body member 37 into alignment.

[0072] The tapered contact also prevents the passage of water withinscrew-threaded aperture 45 and hence reduces the risk of corrosion oflock 36 although, preferably, an anti-corrosive grease would still beapplied to the components of lock 36 to ensure that no corrosion occurs.

[0073] The contact between tapered shoulder portion 40 and taperedrecess 44 also allows for the efficient transfer of any load on headportion 39 to body member 37 rather than to the thread of screw-threadedshaft 41. Hence, the only means by which lock 36 may fail is if headportion 39 is sheared from screw-threaded shaft 41 and it is envisagedthat such a force will not be encountered in normal operation.

[0074] Lock 36 provides for an elegantly simple system for releasablyretaining a wear member to a mounting nose of an excavator bucket. Thelock is relatively cheap to manufacture and is easy to use in the fieldwhile still providing a secure attachment means.

[0075] While resilient plugs may be employed to plug the locking pinapertures of FIGS. 2 to 6 to stop ingress of particulate matter whichmight otherwise constitute an abrasive material, entry of dirt into thesmall spaces between the flat faces of the socket and spigot members ofthe assembly tend to pack tightly and actually prevent relative movementbetween the nose and the wear member thus reducing, rather thanincreasing, internal wear between components.

[0076] Throughout this specification, unless the context requiresotherwise, the word "comprise", and variations such as "comprises" or"comprising", will be understood to imply the inclusion of a statedinteger or group of integers or steps but not the exclusion of any otherinteger or group of integers.

What is Claimed is:
 1. An excavator tooth system comprising: a mountingnose having a projecting spigot; and, a wear member having at one endthereof a socket, said socket being defined by spaced side walls andupper and lower walls converging from a rearwardly facing socket openingto a forward end of said socket, each of said upper and lower wallscomprising a forward bearing face and a rear bearing face separated by aforwardly convergent intermediate face, said front and rear bearingfaces being substantially parallel to a longitudinal axis of said wearmember, and in use, said front and rear bearing faces being engageablewith complementary bearing faces on said spigot.
 2. A system as claimedin claim 1 wherein said forward end of said socket forms an end bearingface.
 3. A system as claimed in claim 2 wherein said end bearing faceextends transversely of said longitudinal axis.
 4. A system as claimedin claim 1 wherein the wear member comprises an adaptor having a frontend adapted for releasable attachment thereto of a digging point.
 5. Asystem as claimed in claim 1 wherein said wear member includes anaperture in at least one wall of said socket.
 6. A system as claimed inclaim 1 wherein said wear member includes aligned apertures on oppositewalls of said socket.
 7. A system as claimed in claim 6 wherein saidaligned apertures extend through opposite side walls of said socket. 8.A system as claimed in claim 1 wherein at least portion of said rearbearing face is of a width greater than said forward bearing face.
 9. Asystem as claimed in claim 1 wherein at least portion of said rearbearing face is of a substantially a similar width to said forwardbearing face.
 10. A system as claimed in claim 1 wherein said rearbearing face is of an area greater than said forward bearing face.
 11. Asystem as claimed in claim 1 wherein said socket opening has atransverse width greater than the width of the forward end of saidsocket.
 12. A system as claimed in claim 1 wherein the side walls ofsaid socket taper convergently towards said forward end of said socket.13. An excavation device having an excavator tooth system according toclaim
 1. 14. An excavation device as claimed in claim 13 wherein saidmounting nose is attached thereto.
 15. An excavation device as claimedin claim 13 wherein said mounting nose is integrally formed therewith.16. A lip for an excavation device having a plurality of spacedexcavator tooth systems according to claim
 1. 17. A lip as claimed inclaim 16 wherein said mounting noses are attached to said lip.
 18. A lipas claimed in claim 16 wherein said mounting noses are integrally formedwith said lip.
 19. A lip as claimed in claim 16 wherein wear plates arereleasably secured between adjacent said spaced mounting noses.
 20. Alock for releasably attaching said wear member to said mounting nose ofthe excavator tooth system of claim 1, said lock comprising: at leastone retaining member having a head portion and a screw-threaded shaft;and an elongate body member having a non-circular cross section, saidbody member being adapted for removable insertion in a lock aperture ofcomplementary cross section in the mounting nose, said body memberincluding at least one screw-threaded aperture to receivably locate saidat least one retaining member, said body member, in use, being captivelyretained in said lock aperture by a partial misalignment between saidlock aperture and a retaining aperture in the wear member when said wearmember is located on said mounting nose, said at least one retainingmember, in use, being releasably securable in said body member via saidretaining aperture whereby said head portion is located within saidretaining aperture to prevent disengagement between said mounting noseand said wear member.
 21. A lock as claimed in claim 20 wherein saidhead portion includes a tapered shoulder extending between said headportion and said shaft, said tapered shoulder in use being frictionallyengageable with a corresponding tapered recess in said body member. 22.A lock as claimed in claim 20 wherein said at least one screw-threadedaperture is displaced from a central longitudinal axis of said bodymember.
 23. A lock as claimed in claim 20 having a corrosion resistantcoating thereon.
 24. A lock as claimed in claim 20 wherein said bodymember is formed from a corrosion resistant material.
 25. A lock asclaimed in claim 20 wherein said body member is formed from a rigidengineering plastics material.
 26. A lock as claimed in claim 20 whereinretaining members are coupled with said body member at opposite endsthereof to secure the wear member on the mounting nose via respectiveretaining apertures in said wear member.
 27. A method of securing saidwear member to said mounting nose of the excavator tooth system of claim1, said method including the steps of: inserting a body member of a lockinto a lock aperture in said mounting nose, said body member having anon-circular cross sectional shape for location in a lock aperture ofcomplementary cross sectional shape in the mounting nose; captivelyretaining said body member in said lock aperture by locating said wearmember on the mounting nose whereby at least one retaining aperture insaid wear member is partially misaligned with said lock aperture in themounting nose; and inserting, via said at least one retaining aperture,a screw-threaded shaft of a retaining member into a screw-threadedsocket in said body member whereby a head portion of said retainingmember is located in said retaining aperture to prevent disengagementbetween said mounting nose and said wear member.
 28. A lock as claimedin claim 27 wherein retaining members are coupled with said body memberat opposite ends thereof to secure the wear member on the mounting nose.